If you develop a fever after returning from a Yellow Fever risk area, treat it as urgent—seek same-day medical care (ER if you feel very unwell or have warning signs) and tell the staff immediately where you traveled, the exact dates, whether you were vaccinated, and any mosquito exposure, because early travel history changes testing and infection-control decisions; go straight to the ER right away if you have severe headache, confusion, shortness of breath, chest pain, persistent vomiting, bleeding/bruising, yellowing of eyes/skin, severe weakness, dehydration, or you’re pregnant/immunocompromised, and until you’re evaluated, avoid mosquito bites (repellent, long sleeves, stay indoors/screens) so you don’t potentially pass an infection to local mosquitoes, and do not take aspirin/ibuprofen unless a clinician says it’s safe (use acetaminophen/paracetamol for fever instead).